Accused of killing Caylee in June 2008 and dumping her body in the woods near her home (where it was found months later), Casey was eventually acquitted of the murder charges and convicted instead of four misdemeanor counts of lying to the police.

Casey originally claimed the little girl had been abducted by her nanny (who might not even exist), though she inexplicably didn't report her daughter's disappearance at first. The defense theorized that Caylee drowned accidentally while swimming in the family's pool unsupervised, and that the abduction story was a panicked attempt at a cover-up. There are many people, however, who dispute this idea -- and Casey's father George is one of them.

"I don't believe [the drowning]. That's a bunch of bull to me," he said in the ID special.

"That's too easy of a story to bring up 'cause if that would've happened, I think my daughter would've at least had the common decency or common sense inside to call 911 and say something. That's a bunch of crap."

George has his own hypothesis when it comes to what happened to his granddaughter, and it's a very disturbing one (though also seemingly plausible). He claimed that there were times when Caylee slept for remarkably long periods of time, sometimes up to 13 hours, and he suspected that Casey gave her daughter medication to knock her out -- saying that her friends had access to drugs like Xanax, which he referred to by the street name "Zanny."

(In an extremely odd coincidence, "Zanny the nanny" was a nickname Casey used for the babysitter she accused of kidnapping Caylee, Zenaida Gonzalez. When police investigated Gonzalez, however, they found that no one by that name lived where Casey said she lived -- and when they located a woman by that name, she didn't match Casey's description and said she didn't know her or Caylee.)

George's theory is similar to what the judge who presided over the trial recently said he believed happened to Caylee, which is that Casey accidentally killed her using chloroform in an attempt to make her go to sleep. It differs drastically, however, from what George's wife believes.

Cindy, for her part, agrees with the defense about the accidental drowning and subsequent cover-up.

"I don't know what distracted her or what happened," she said, "but, as far as being responsible, I feel like it was an accident.”

"Emotionally, something happened to her when she realized her child had died, that she couldn't cope with that. And, she panicked, and I think that happens to a lot of people that sometimes you're worried that someone's not going to believe you that it was an accident so you try to make it look like something else."

Cindy also said that she and her daughter do communicate from time to time, but George and Casey are not in contact. In fact, he thinks she should be "behind bars" and "suffer like ... Caylee suffered."

"She's somewhere in Florida from what I understand," he said. "Whatever life she has, I hope she makes something positive for it. Am I ever gonna speak to my daughter again? No. We're done because when all this stuff happened, I lost my daughter and my granddaughter. I lost them both."

Whoa. So, clearly this couple is dealing with the unspeakable tragedy that's been haunting them for years in very, very different ways. This isn't completely shocking, given the sexual abuse allegations that Casey made against her father during her trial (whether or not they were true, the fact that she made them doesn't speak well of their relationship). But it does seem rather significant that George (a former police officer) is willing to believe that his own daughter killed his granddaughter, albeit accidentally. (That's the one thing George and Cindy's theories have in common -- neither one of them thinks Casey deliberately murdered her child.)

At this point, it seems likely that the world may never know what truly happened to Caylee Anthony. Even her own grandparents can't agree on how that little girl died -- the little girl they called "the light of [their] lives." Ultimately, nothing is going to bring Caylee back. But that doesn't mean she doesn't deserve justice. Will she ever get it?